I've bought the amazing GODOX AD400PRO with Elinchrom mount. But I soon realized, that I cannot use my Elinchrom deflectors anymore. The AD400PRO is missing the mounting hole. I've designed and 3d printed brackets on my Prusa i3 MK3 from white PETG that work really well holding the deflector in place. Mount the deflector in normal orientation (concave side facing flash-tube). See which light characteristics you want. I prefer position 3.
More info on my blog: www.schweinert.com